Relay station attack prevention

ABSTRACT

A system includes a plurality of antennas, an access control mechanism, and a computing resource. The computing resource is configured to initiate each of multiple antennas to transmit a wireless signal and receive values indicative of signal strength of the wireless signals from the multiple antennas. The computing resource also is configured to calculate a position of a wireless electrical device based on the received values and calculate an error value of the calculated position of the wireless electrical device. Further, the computing resource is configured to determine that the error value is greater than an error threshold and to disable the access control mechanism.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.62/954,755, filed Dec. 30, 2019, which is hereby incorporated byreference in its entirety.

BACKGROUND

Contactless wireless security systems, including automotive keylessentry systems, such as Passive Entry/Passive Start (PEPS) systems, facea threat referred to as a “relay attack” or “relay station attack,”which may result in the theft of a vehicle without the owner'sawareness. A relay attack may involve two individuals, although anynumber of individuals may be utilized, working in cooperation with eachother. Each of the two individuals carries a device (referred to as anattack kit) capable of receiving a signal from either the vehicle or thevehicle's key fob and forwarding the received signal to the otherindividual after amplifying the signal. In one scenario, the individualsfollow the vehicle and its driver. The driver stops at, for example, astore or a restaurant. Individual-1 stands adjacent to the parkedvehicle while individual-2 follows and stands next to the owner of thevehicle (who may be inside the store or restaurant or any other locationaway from the car). Individual-1 initiates a door unlock operation bytouching the car handle, pulling the car handle, or pushing a button onthe car, which normally requires a valid key fob to be within a certaindistance of the door. Upon initiating the unlock operation, the vehiclebroadcasts a wireless signal intended for reception by a valid, nearbykey fob.

The attack kit carried by individual-1 picks up the wireless signalbeing broadcast by the vehicle and relays the signal (such as physicallayer signals or encrypted bit streams) to the attack kit ofindividual-2. Upon receiving the signal from the attack kit ofindividual-1, the attack kit of individual-2 replicates the signal inthe format commensurate with the key fob and transmits the replicatedkey fob-compliant signal to the key fob carried by the vehicle's owner(which presumably is within sufficient range of individual-2); therebywaking up the key fob. The key fob which receives the wireless signaland cannot distinguish individual-2's attack kit from the vehicle itselfconsiders the attack kit carried by individual-2 as the vehicle, and, asit is configured to do, transmits a wireless response signal toauthenticate the key fob to the vehicle. This response signal is thenreceived by the attack kit of individual-2 which relays the signal backto the attack kit of individual-1. The attack kit of individual-Ireceives the response and replicates a wireless signal compatible withthe vehicle. The vehicle's wireless communication system cannotdistinguish a wireless signal from the attack kit of individual-1 fromthe key fob itself and performs the designated operation (e.g., unlocksthe door).

SUMMARY

In one example, a system includes a plurality of antennas, an accesscontrol mechanism, and a computing resource. The computing resource isconfigured to initiate each of multiple antennas to transmit a wirelesssignal and receive values indicative of signal strength of the wirelesssignals from the multiple antennas. The computing resource also isconfigured to calculate a position of a wireless electrical device basedon the received values and calculate an error value of the calculatedposition of the wireless electrical device. Further, the computingresource is configured to determine that the error value is greater thanan error threshold and to disable the access control mechanism.

In another example, a method includes initiating each of multipleantennas to transmit a wireless signal. The method also includesreceiving values indicative of signal strength of the wireless signalsfrom the multiple antennas and calculating a position of a wirelesselectrical device based on the received values, the calculated positionwithin a threshold distance. Further, the method includes calculating anerror value of the calculated position of the wireless electrical device(the calculated error value to be less than an error threshold) andenabling an access control mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various examples, reference will now bemade to the accompanying drawings in which:

FIG. 1 shows an illustrative diagram for an arrangement of a contactlesswireless security system in accordance with various examples.

FIG. 2 depicts a possible configuration for caring out a relay attack.

FIG. 3 illustrates a vehicle with a control circuit in accordance withan example.

FIG. 4 illustrates additional detail of the control circuit 310 and akey fob in accordance with an example.

FIG. 5 illustrates an example of a determination of the location of awireless device relative to a vehicle for which an error value isrelatively low.

FIG. 6 illustrates an example of a determination of the location of awireless device relative to a vehicle for which the error value isrelatively large.

FIG. 7 shows an example of a method performed by the control circuit ofFIG. 2.

DETAILED DESCRIPTION

FIG. 1 shows an illustrative diagram for an arrangement of a contactlesswireless security system 100 in accordance with various examples. Theexample of FIG. 1 illustrates a passive entry/passive start (PEPS)system for a vehicle 102. The vehicle 102 includes multiple antennas 104installed at various locations around the vehicle. As illustrated inFIG. 1, vehicle 102 may be a vehicle in which wireless antennas 104 areinstalled around the vehicle (e.g., inside each door near the doorhandles, in the trunk, etc.).

FIG. 1 also shows a wireless key fob 120 (or other type of wirelesselectrical device). Wireless key fob 120 may be implemented as portabledevice to permit an individual to carry the key fob 120 on their person(e.g., pocket, purse, etc.). Key fob 120 may be configured to lock andunlock a door or the trunk of vehicle 102 and/or to start the vehicle.Key fob 120 performs wireless communication with one or more of wirelessantennas 104 when key fob 120 is close enough to vehicle 102 such thatvehicle 102 is within wireless range of key fob 120. Key fob 120authenticates itself to vehicle 102. After a determination that key fob120 is authentic, vehicle 102 may provide the desired functionality(e.g., door locking, unlocking, engine starting, etc.).

Each antenna 104 has the capability of transmitting a challenge message101 to key fob 120. In some examples, challenge message 101 includes asignal which is received by key fob 120 if key fob 120 is withinwireless range of at least one of the antennas 104. Challenge message101 may cause key fob 120 to transmit a response message 107. Theresponse message 107 may be received by a different antenna than thetransmission 104 of vehicle 102, and the receiving channel may be at adifferent frequency than the transmission channel on which the challengemessage 101 was sent. The response message 107 provides credentials tovehicle 102 allowing vehicle 102 to authenticate key fob 120, and thus,allow vehicle 102 to provide the desired functionality (e.g., unlockdoors, start the engine, etc.).

FIG. 2 depicts a possible configuration for carrying out a relay attack.Relay attack kit 106 acts as an emulator for key fob 120 and relayattack kit 108 acts as an emulator for vehicle 102. The attack kits 106and 108 communicate with each other through transmission link 103. Morespecifically, attack kit 106 is brought by an individual to a locationin sufficiently close proximity to vehicle 102 to receive challengemessage 101 from one of wireless antennas 104 (i.e., is close enoughsuch that attack kit 106 may communicate wirelessly with vehicle 102).Attack kit 106 then may receive challenge message 101 from vehicle 102whenever vehicle 102 transmits challenge message 101. Vehicle 102 maycontinuously transmit challenge message 101 or vehicle 102 may transmitchallenge message 101 in response to an outside action, such as touchingvehicle 102 at location 150, detection by vehicle 102 of movement inclose proximity to vehicle 102, pushing a button, or by other mechanismsto initiate the challenge-response protocol.

Once challenge message 101 begins transmitting, attack kit 106 relayschallenge message 101, via transmission link 103, to attack kit 108.Attack kit 108 is within close proximity of key fob 120 (i.e., is closeenough such that attack kit 108 may communicate wirelessly with key fob120). Upon receiving challenge message 101 from attack kit 106 throughtransmission link 103, attack kit 108 generates signal 105 to bereceived by key fob 120. Signal 105 is a copy of challenge message 101after being relayed by attack kit 106 to attack kit 108. Key fob 120receives signal 105 from attack kit 108 and, unaware, that the signaloriginated from attack kit 108 instead of a vehicle 102, starts toauthenticate itself to vehicle 102 by transmitting the response message107 to what it believes is a valid challenge message.

Sharing the same operational principle described above, attack kit 108emulating vehicle 102, relays response message 107 to attack kit 106 viatransmission link 103. Attack kit 106 transmits signal 109 copying thecontent of the response message 107 from key fob 120. In another attackexample, response message has a large enough range that so that attackkits 106 and 108 may not be needed to relay the response message 107back to the vehicle. Further, in some implementations a response message107 is not needed at all. Vehicle 102 receives signal 109, which is acopy of response message 107 to the challenge message 101 and uses thereceived signal to perform an authentication process. Once theauthentication (of presumed key fob 120) is successful, the individualutilizing attack kit 106 will be able to achieve the desired result(e.g., door locking, unlocking, engine starting). This relay attack mayoccur despite key fob 120 being so far from vehicle 102 so as not to bein direct communication with vehicle 102. That is, transmission link 103between attack kits 106 and 108 may have at least one bi-directionaltransmission channel of a type that allows there to be a distancebetween the attack kits 106 and 108 that is greater than the maximumdistance over which the wireless antennas 104 of vehicle 102 candirectly communicate with key fob 120.

FIG. 3 illustrates a vehicle 302 with antennas 303, 304, 306, and 308,control circuit 310, and access control mechanism 320. While fourantennas 303-308 are shown in this example, any suitable number ofantennas are possible. The antennas 303-308 are mounted within vehicle302 at the locations as shown or at different locations within thevehicle 302. At least two of the antennas are oriented orthogonal toeach other. As shown in this example, antenna 308 is mounted orthogonalto antennas 303, 304, and 306. The control circuit 310 is electricallyconnected to each of the antennas 303-308 through correspondingconductors 301, 309, 305, and 307. The control circuit 310 can causeeach antenna 303-308 to separately transmit a wireless signal therefrom.That is, the control circuit 310 can transmit a signal over conductor301 to antenna 303 to cause antenna to transmit a wireless signal.Similarly, the control circuit 310 can cause each of the other antennas304-308 to transmit wireless signals. The control circuit 310 may causeonly one antenna at a time to transmit a wireless signal or may causetwo or more antennas to concurrently transmit wireless signals. If thecontrol circuit 310 operates each antenna separately, then each antennacan transmit a wireless signal at the same frequency. If two or moreantennas are used to concurrently transmit wireless signals, then thecontrol circuit 310 causes the antennas to use different frequencies toavoid interference.

The access control mechanism 320 is coupled to the control circuit 310and controls one or more functions of the vehicle 302 such as unlockingthe doors and/or permitting the vehicle's motor to be started. For avehicle with an internal combustion engine, the access control mechanism320 permits the engine to be started such as by turning a key in theignition or pressing a “start” button. For an electric vehicle, theaccess control mechanism 320 permits the vehicle's electric motor to beactivated.

FIG. 4 is an example illustrating additional detail for the key fob 120and the various electronic systems within the vehicle 302. In thisexample, the control circuit 310 of the vehicle 302 includes a controlunit 410, a transceiver 420, a receiver 430, and a trigger 440. Thetrigger 440 represents any source or signal to start the communicationdescribed herein, for example, touching a door handle, a periodic timer,etc. An antenna 432 is coupled to the receiver 430. The antennas 303,304, 306, and 308 are coupled to the transceiver 420. The access controlmechanism 320 is coupled to the control unit 410. The control unit 410includes one or more processors 412 (also referred to as a computingresource) coupled to a non-transitory storage device 414. Non-transitorystorage device 414 may comprise volatile storage (e.g., random accessmemory), non-volatile storage (e.g., a solid-state storage drive,read-only memory, etc.), etc. The non-transitory storage device 414stores executable code 420, which is executable by processor(s) 412.

The key fob 120 includes a microcontroller unit (MCU) 460, an analogfront end (AFE) 462, a transmitter 464, an antenna 465 coupled to thetransmitter 464, and antennas 470 coupled to the AFE 462. A set ofbuttons 465 are coupled to the MCU 460 and used for remote keyless entry(RKE) such as manual unlocking of the vehicle without a distancemeasurement. The MCU 460 may include one or more processors, memory,etc. The MCU 460 may cause transmitter 464 to transmit a wireless signalto antenna 432. Bidirectional signals can be transmitted betweenantennas 303-308 and antennas 370 within the key fob 120. Three antennas470 are shown in the example of FIG. 4, and the three antennas 470 arepositioned within a housing of the key fob such that the antennas 470are orthogonal to each other.

The wireless channel 445 between transmitter 464 and receiver 430 may bean ultra-high frequency (UHF) channel (e.g., 315 MHz, 433 MHz, etc.).The wireless channel 446 between the AFE 462 and transceiver 420 maycomprise a lower frequency channel (e.g., 100-200 KHz). Channel 445 canbe used for an authentication process, that is, for the key fob 120 tobe authenticated to the control circuit 310. Channel 446 may be used, asdescribed herein, to determine the location of the key fob 120 relativeto the vehicle 302 and an error value calculated for the determinedlocation of the key fob 120.

As explained above, the three antennas 470 of the key fob 120 arearranged orthogonal to each other (e.g., x, y, z axes). Each antenna 470is unidirectional meaning that the antenna is more sensitive to wirelesssignals from one direction than another/orthogonal direction. Becausethe key fob 120 has three orthogonally-arranged antennas 470, at leastone of the three antennas will be able to detect a signal from a givenvehicle antenna 303-308 regardless of the physical orientation of theportable key fob 102 relative to the vehicle. That the key fob 102 hasthree orthogonally-arranged antennas 470 can be used by the controlcircuit 310 to accurately determine the location of the key fob.

FIG. 5 shows an example of a determination of a key fob relative tothree vehicle antennas 502, 504, and 506, with antenna 506 arrangedorthogonal to antennas 502 and 504. The orientation of an antenna refersto the fact that a given antenna is more sensitive to wireless signalsreceived at the antenna from one direction than from another direction.The control circuit 310 causes (e.g., processor(s) 412 executingexecutable code 420) each of the antennas 502, 504, and 506 to transmita wireless signal for detection by the key fob's antenna(s) 470. In oneexample, the control circuit 310 may sequentially cause each antenna 502to 506 to transmit a signal. In other examples, the control circuit 310may concurrently cause antennas 502, 504, and 506 to transmit signals(e.g., at different frequencies) for detection by the key fob 102.

If the key fob 102 is within wireless range of the vehicle (e.g., within30 feet), the key fob 102 detects the signals from the antennas 502-506.The strength of the wireless signal detected by the key fob form a givenantenna 502-506 is a function, at least in part, of the distance betweenthe key fob and the respective antenna 502-506. The detected signalstrength may the average or root mean square (rms) of the current orvoltage from each of the key fob's antennas 470. In other example, thedetected signal strength may the largest current or voltage from thethree antennas 470. The detected signal strength is thus a proxy fordistance between the key fob 102 and the antenna. In the example of FIG.5, the strength of the signal from antenna 502 and received by the keyfob 102 is at a level that means that the key fob is a distance D1 fromantenna 501. Distance D1 defines the radius of circle 522 centered onantenna 502. In these examples, the location of points at the same fieldstrength is shown as a circle for simplicity but may be ellipticalinstead. The antennas described herein are more sensitive to wirelesssignals received at the antenna from one direction than another, andthus the shape of the common field strength lines are generallyelliptical. Similarly, based on the strength of the signals detected bykey fob 102 from the other antennas 504 and 506, key fob 012 isdetermined to be a distance D2 from antenna 504 and D3 from antenna 506.Distance D2 defines the radius of circle 523 centered on antenna 504.Distance D3 defines the radius of circle 524 centered on antenna 506.The locations of the antennas 502-506 are fixed within the vehicle andthus the circles 522-524 relative to the vehicle can be determined. Inone example, a coordinate system for the vehicle is predefined with theorigin of the coordinate system being at a predetermined location withthe vehicle.

In one implementation, the key fob 102 transmits the signal strengthvalues via transmitter 464 to receiver 430 to thus be received by theprocessor(s) 412. In another example, the key fob's MCU 460 converts thedetected signal strengths to distance values and transmits the distancevalues to the processor(s) 412. The three circles 522, 523, and 524 havean overlap region 550. The processor(s) 412 calculate the geometriccenter 560 of the overlap region as being the presumed location of thekey fob 102. The calculated center 560 is calculated relative to theorigin of the vehicle's predefined coordinate system.

With the three orthogonally-arranged antennas 470 of the key fob 102,the accuracy of the calculation of the key fob's location is relativelyhigh. That is, the size of the overlap region 550 is relatively small.The processor(s) 412 calculates the location of the key fob 102 and alsocalculates an error value associated with the calculated location. Inone example, to calculate the error value, the processor(s) 412calculates, for each antenna 502-506, the difference between (a) thedistance from the antenna to the key fob and (b) the distance betweenthe antenna and the calculated key fob location 560. In FIG. 5, forexample, the distance from antenna 502 to the key fob is D1 and thedistance between the antenna 502 and the calculated key fob location 560is D2. The aforementioned difference for antenna 502 is D1−D2=D3. D3represents the individual error for the key fob location based on thesignals received from antenna 502 by the key fob. Similarly, thedistance from antenna 504 to the key fob is D11 and the distance betweenthe antenna 504 and the calculated key fob location 560 is D12. Theaforementioned error difference for antenna 504 is D11−D12=D13. Further,the distance from antenna 506 to the key fob is D21 and the distancebetween the antenna 506 and the calculated key fob location 560 is D22.The error difference for antenna 506 is D21−D22=D23.

The error value may be calculated by the processor(s) 412, for example,as the square root of the sum of squares of the error differences, thatis, the sum of squares between (a) the calculated distances between themultiple antennas 502-506 and the key fob 102 and (b) the calculateddistances of the multiple antennas to the calculated position 560 of thekey fob. In the example of FIG. 5, the error value is:

ERROR VALUE=√{square root over (D3² +D13² +D23²)}  (1)

FIG. 6 illustrates an example similar to FIG. 5, but instead of using athree-antenna key fob 120, a single axis wireless device is used such asmight be used in an attempt to open the vehicle door and/or start thevehicle. Because the wireless access device is a single-axis device, thedevice's antenna will likely be oriented with regard to at least one ofthe antennas 502, 504, and 506 such that the strength of the wirelesssignal from the antenna is relatively weak. This situation isillustrated in FIG. 6 as the signal received by the single-axis devicefrom antenna 506 is weaker than was the case for the three-axis key fobof FIG. 5. The signal strength values from the single-axis device aretransmitted to the control circuit 310 within the vehicle. The controlcircuit 310 uses the received signal strength values to determine thedistance from each antenna 502-506 to the wireless device. In theexample of FIG. 6, the determined distances from antenna 502 and 504 tothe wireless device is D1 and D11, respectively, as was the case forFIG. 5.

The determined distance from antenna 506 to the wireless device is D31,which is larger than D21 (FIG. 5). Thus circle 524 centered on antenna506 has expanded out to circle 624 as shown in FIG. 6. The radius ofcircle 624 is D31. As such, the overlap region 650 among the threecircles 522, 523, and 624 is shown at 650 and is larger than overlapregion 550 of FIG. 5. The processor(s) 412 calculate the geometriccenter of the overlap region 650. Reference numeral 660 identifies thelocation of the geometric center of the overlap region 650. For antenna502, the error value is shown as D4 (D1 minus the distance from antenna502 to location 660). For antenna 504, the error value is shown as D14(D11 minus the distance from antenna 504 to location 660). Similarly,for antenna 506, the error value is shown as D33 (D31 minus the distancefrom antenna 506 to location 660). The calculated error value based onthe three individual error values is:

ERROR VALUE=√{square root over (D4² +D14² +D33²)}  (2)

Comparing FIG. 6 to FIG. 5, because D4 (for antenna 502) is larger thanD3, D14 (for antenna 504) is larger than D13, and D33 (for antenna 506)is larger than D23, the overall computed error for FIG. 6 is larger thanthe corresponding error value for FIG. 5.

To enable the access control circuit 320 to unlock the doors of thevehicle 302 and/or to enable the vehicle's motor, the processor(s) 412determine whether at least both of the following conditions are true.First, the wireless device which receives signals from the vehicle'santennas is determined to be less than a distance threshold. Second, theerror value computed for the wireless device is determined to be lessthan an error threshold value. That is, the wireless device is fairlyclose to the vehicle (e.g., within 30 feet) and the error value isrelatively small. The distance and error thresholds may be preset andapplication specific.

With regard to the example of FIG. 5, the computed distance of location560 relative to vehicle 302 is determined to be less than the thresholddistance, and the computed error value (Eq. (1) above) is determined tobe less than the error threshold value. As such, the control circuit 310will cause the access control circuit 320 to be activated to, forexample, unlock the doors and/or enable the motor.

In the example of FIG. 6, however, while the computed distance oflocation 660 relative to vehicle 302 is determined to be less than thethreshold distance, the computed error value (Eq. (2) above) isdetermined to be greater than the error threshold value. As such, thecontrol circuit 310 will not cause the access control circuit 320 to beactivated and thus, the either or both of the doors will remain lockedand the vehicle's motor will not be engaged.

FIG. 7 illustrates an example method to determine whether the enable theaccess control mechanism 320 or disable or keep disabled the accesscontrol mechanism. At 702, the method includes starting theauthentication process. This operation may be performed as a wirelessdevice (e.g., legitimate key fob for the vehicle or a fraudulent device)is brought close enough to the vehicle to detect wireless signals fromthe vehicle's antennas. At 704, the method includes the control circuit310 causes each of multiple antennas within the vehicle to transmit awireless signal (simultaneously or sequentially).

At 706, the wireless device receives the wireless signals and determinesthe strength of each wireless signal. The wireless device then transmitsthe signal strength values to the control circuit 310 via transmitter464 and receiver 430. At 708, the control circuit 310 (e.g., itsprocessor(s) 412) calculates, as explained above, the position of thewireless device (and thus the distance to the vehicle) and thecorresponding error value.

If, at 709, the distance is greater than a distance threshold value (avalue corresponding to, for example, 30 feet), then control loops backto 704. Otherwise (when the distance is less than the distancethreshold), control passes to 910.

If the calculated error value is less than the error threshold value (asdetermined at 710), then at 712, the control circuit 310 enables theaccess control mechanism 320. However, if the error value is greaterthan the error threshold value, then the access control mechanism is notenabled. In the example of FIG. 7, the access control mechanism isaffirmatively disabled at 716 following at least n failed attempts asdetermined at 714. That is, the access control mechanism may not bedisabled just on the basis of determining once that the error value isgreater than the error threshold value. In the example of FIG. 7, theaccess control mechanism is disabled at 716 upon the occurrence of three(n equals 3) times that the calculated error value is greater than theerror threshold.

The term “couple” is used throughout the specification. The term maycover connections, communications, or signal paths that enable afunctional relationship consistent with the description of the presentdisclosure. For example, if device A generates a signal to controldevice B to perform an action, in a first example device A is coupled todevice B, or in a second example device A is coupled to device B throughintervening component C if intervening component C does notsubstantially alter the functional relationship between device A anddevice B such that device B is controlled by device A via the controlsignal generated by device A.

Modifications are possible in the described embodiments, and otherembodiments are possible, within the scope of the claims.

What is claimed is:
 1. A non-transitory storage device including machineexecutable instructions which, when executed by a computing resource,cause the computing resource to: initiate each of multiple antennas totransmit a wireless signal; receive values indicative of signal strengthof the wireless signals from the multiple antennas; calculate a positionof a wireless electrical device based on the received values; calculatean error value of the calculated position of the wireless electricaldevice; determine that the error value is greater than an errorthreshold; and disable an access control mechanism.
 2. Thenon-transitory storage device of claim 1, wherein the machine executableinstructions, when executed by the computing resource, cause thecomputing resource to calculate the position of the wireless electricaldevice through use of the received values to calculate a distancebetween the wireless electrical device and each antenna.
 3. Thenon-transitory storage device of claim 2, wherein the machine executableinstructions, when executed by the computing resource, cause thecomputing resource to calculate the position of the wireless electricaldevice based on the calculated distances of the wireless electricaldevice to each antenna of the multiple antennas.
 4. The non-transitorystorage device of claim 2, wherein the machine executable instructions,when executed by the computing resource, cause the computing resource tocalculate the error value based on the calculated distances of thewireless electrical device to each antenna of the multiple antennas. 5.The non-transitory storage device of claim 2, wherein the machineexecutable instructions, when executed by the computing resource, causethe computing resource to calculate the error value as a square root ofa sum of squares of differences between (a) the calculated distances ofthe multiple antennas to the wireless electrical device and (b) thecalculated distances of the multiple antennas to the calculated positionof the wireless electrical device.
 6. The non-transitory storage deviceof claim 1, wherein the multiple antennas comprise at least fourantennas.
 7. The non-transitory storage device of claim 1, wherein themachine executable instructions, when executed by the computingresource, cause the computing resource to disable activation of anaccess control mechanism of a vehicle motor.
 8. A method, comprising:initiating each of multiple antennas to transmit a wireless signal;receiving values indicative of signal strength of the wireless signalsfrom the multiple antennas; calculating a position of a wirelesselectrical device based on the received values, the calculated positionto be within a threshold distance; calculating an error value of thecalculated position of the wireless electrical device, the calculatederror value to be less than an error threshold; and enabling an accesscontrol mechanism.
 9. The method of claim 8, wherein calculating theposition of the wireless device includes calculating the position of thewireless electrical device by using of each antenna's wireless signal tocalculate a distance between the wireless electrical device and therespective antenna.
 10. The method of claim 9, wherein calculating theposition of the wireless device includes calculating the position of thewireless electrical device by calculating distances of the wirelesselectrical device to the multiple antennas.
 11. The method of claim 9,wherein calculating the error value comprises calculating the errorvalue based on the calculated distances of the wireless electricaldevice to the multiple antennas.
 12. The method of claim 9, whereincalculating the error value comprises calculating a sum of squares ofdifferences between (a) the calculated distances of the multipleantennas to the wireless electrical device and (b) the calculateddistances of the multiple antennas to the calculated position of thewireless electrical device.
 13. The method of claim 8, furthercomprising disabling the access control mechanism responsive to (a) theposition of the wireless electrical device being within the thresholddistance and (b) the error value being greater than the error threshold.14. A system, comprising: a plurality of antennas; an access controlmechanism; and a computing resource coupled to the plurality of antennasand to the access control mechanism, the computing resource isconfigured to: initiate each of multiple antennas to transmit a wirelesssignal; receive values indicative of signal strength of the wirelesssignals from the multiple antennas; calculate a position of a wirelesselectrical device based on the received values; calculate an error valueof the calculated position of the wireless electrical device; determinethat the error value is greater than an error threshold; and disable theaccess control mechanism.
 15. The system of claim 14, wherein the systemis a vehicle, the vehicle includes a door, and wherein the accesscontrol mechanism is configured to lock and unlock the door.
 16. Thesystem of claim 14, the computing resource is configured to calculatethe position of the wireless electrical device through use of eachantenna's wireless signal to calculate a distance between the wirelesselectrical device and the respective antenna.
 17. The system of claim16, wherein the computing resource is configured to calculate theposition of the wireless electrical device based on the calculateddistances of the wireless electrical device to the multiple antennas.18. The system of claim 16, wherein the computing resource is configuredto calculate the error value based on the calculated distances of thewireless electrical device to the multiple antennas.
 19. The system ofclaim 16, wherein the computing resource is configured to calculate theerror value as a square root of sum of a squares of differences between(a) the calculated distances of the plurality of antennas to thewireless electrical device and (b) the calculated distances of theplurality of antennas to the calculated position of the wirelesselectrical device.
 20. The system of claim 14, wherein the plurality ofantennas comprises at least four antennas.